جستجوی مقالات مرتبط با کلیدواژه « آبشویی » در نشریات گروه « جنگلداری »

The utilization of wood is limited due to its vulnerability to moisture, dimensional changes, and susceptibility to both living organisms and environmental factors. One method of wood enhancement involves impregnating the wood with various aminic resin monomers and subsequently converting them into polymers within the wood structure. This study aims to enhance the physical properties of poplar (Populus deltoides)  wood by employing MF resin for saturation. Additionally, a 5% boric acid solution is utilized during saturation to enhance resistance against fungal decay. The first part of the study involved saturating wood samples with different concentrations (7%, 15%, 27%, and 35%) of MF resin, using the vacuum/pressure technique, and examining the properties of the treated wood. In the second part, samples were treated with resins made at different molar ratios to investigate the impact of free formaldehyde and other additives on decay resistance. Results revealed a substantial increase in weight gain percentage as resin concentration increased during wood saturation. The impregnation of wood with MF resin and subsequent polymer formation within the wood structure, even after leaching procedure in accordance with EN 84 standard, significantly improved the samples' resistance against white rot decay. Treatment with different resin concentrations considerably enhanced pine wood's resistance to decay. Resins with higher formaldehyde ratios and the inclusion of boric acid as an additional protective measure did not significantly impact the decay resistance of the treated samples. The findings of this study underscore the considerable potential of using MF resin to boost wood's resistance against decay.

Tannin is a natural polymer that has recently been proposed for wood protection, but the structure of this polymer is not resistant to water and can be easily hydrolyzed or leached out from the wood. The use of various aldehydes to synthesize tannin-based resins and therefore improving the properties of these resins has already been studied. Furfural is a natural aldehyde and is the raw material for the production of furfuryl alcohol that is produced from the acidic hydrolysis of agricultural wastes, such as sugarcane. In this study, first, the effect of adding furfural on the tannin network features was investigated. Then, the ability of tannin/furfural natural resin was evaluated to impregnate and modify poplar wood to improve its physical properties and hygroscopic behavior.

Tannin-based resins were made with 20% m/m tannin and different ratios of furfural (2.5, 5, 10, 15, 20, 25, 40, and 50% of tannin dry weight) in different acidic conditions (pH 2, 4.5, 7, 9). For all formulations, the properties of resins were evaluated, including impregnation abilities, leaching resistance, viscosity, density and gel time. Optimal condition for making suitable resin to impregnate wood was selected by the complete factorial method using mini-tab software at a 95% confidence level. Then, the resin made under optimal condition was used to impregnate the poplar wood using the vacuum/pressure method. Heating was used to cure the resin and turn it into a polymer inside the wood. The physical properties of modified wood were measured according to ISO 13061 standard.

Examination of resin properties showed that with an increase in furfural ratio, the resin density increases. Moreover, the resin gel time and viscosity increased, with increasing furfural ratio and acidity respectively. The highest leaching resistance of resin was obtained with a resin made with 50% of furfural. Microscopic studies showed that resins containing furfural had a more porous structure. Thermogravimetric analysis showed that up to 580 °C, tannin / furfural modified polymer had higher thermal stability. According to the complete factorial method used, the optimal condition of resin manufacturing was adding 50% of furfural to tannin with an acidity of 4.5. Samples impregnated with the selected resins had less water absorption and swelling than the untreated ones. The volumetric swelling and water absorption of treated samples showed a considerable decrease with increasing resin concentration.

Extensive studies are underway worldwide to use natural polymers as wood preservatives or modifiers. The results of this study showed that the use of natural tannin / furfural resin has a promising prospect for improving the physical properties of wood. By accurately ‎adjusting the resin manufacturing conditions and the tannin-furfural pretreatment, a resin with suitable viscosity and leaching resistance can be achieved to be used in the wood impregnation industry. It is suggested that future studies investigate the conferred durability and mechanical properties of woods treated and modified with tannin / furfural polymer.

The objective of this research is characterizing the effect of Nano-Zinc oxide (nano-ZnO) dispersions on leach resistance and contact angle of beech wood (Fagus orientalis Lipsky). The Beech wood was cut into standard dimension, and oven dried after treating with nano-Zno solution, based on immersion method. Three treating nano-Zno solution levels: (o, 20000 and 40000 ppm), and two thermal treating levels: (60 and 120 ºC), were selected. After conditioning, leaching tests were performed and contact angle of samples after 1 and 10 seconds were measured. The results showed that by increasing of the nano material concentration and the temperature, the contact angle increased. In tenth second, the minimum and maximum angles were 53.30º and 90.07º which observed for untreated sample and for 40000 ppm concentration and 120ºC temperature, respectively. Improving on contact angle represents the significant reduction in wettability property of surface in treated wood. Results of leaching test implied that effect of increment of nano-zno concentration was negligible, while the temperature increasing resulted in nano-ZnO stabilization.

In forest ecosystems, there is an important interaction between hydrological cycle and nutrient contents. Rainfalls not only have an important role for entrance of nutrient contents to forest ecosystem, but also have an important role to transfer elements from canopy to forest floor and soil. This study performed to investigate the effect of throughfall and forest floor leachate on base-cations dynamics in a mixed hyrcanian beech forest in Golestan province. Throughfall and forest floor leachate samples were taken through 6 months (winter and spring 2008). Amount of base-cations (Ca2+, Mg2+, Na+ and K+) were compared by T-Test between rainfalls and throughfall. Results showed that the amount of Ca2+, Mg2+, Na+ and K+ contents in throughfall were higher than rainfall (p<0.05). Also total content of Mg2+ in throughfall and forest floor leachate compared to rainfall was higher, while Ca2+ and Na+ were lower, significantly (p<0.05). Finally, amount of base-cations were compared by T-Test between throughfall and forest floor leachate. Results showed that the amount of Na+, Ca2+ and K+ contents in throughfall were higher than that of forest floor leachate (p<0.05). In total, canopy and forest floor leaching have added 5.53, 12.42, 3.01 and 1.06 (Kg ha-1 month-1) Na+, K+,Ca2+ and Mg2+, respectively to the soil that were about 97, 202, 137 and 186 percent of the amount of those cations in the rainfall. Therefore, nutrient elements leaching cause soil fertility and increasing of forest products in a short time.